Question

The male gametes of rice plants have 12 chromosomes in their nucleus. The chromosome number in the female gamete, zygote and the cells of the seedling will be __________ respectively.
a. 12,24,12
b. 24,12,12
c. 12,24,24
d. 24,12,24

Answer 1

Hint Here the basic concept of chromosome during fertilization is used. As male and female gametes fuse to form zygotes that are diploid, obviously the chromosome number in the zygote will be doubled. So using this concept anyone can answer this question. The male and female chromosome number remains the same.

Complete answer:
Here in the question, the chromosome number of the male gamete of the rice plant is already given, that is 12 chromosomes in number.
In fertilization events we know that the male gamete fuses with the female gamete to form a zygote.

When we see the chromosome number of the parents that means the male and female gametes, it is always considered as “n”. So as per the question, male gametes have 12 number of chromosomes, hence n= 12 here. Then the female will also be “n”.

So the total number of chromosomes in the female gamete will be n= 12. We got our first blank answer that is 12.

The second blank answer will be 24 as because, here in the question it is asked for the chromosomes in the zygote formed, as in the case of zygote, the “n” gets doubled or can be said it is diploid, because during fertilization the male and female gametes fuse with each other so in this case, the chromosome number gets doubled, so it can be considered as $n + n = 2n$.

The correct answer for this blank will be then 24. Then for the last blank it is asked for the chromosome number in case of cells of the seedling, that is 24.

Hence, The correct answer for this question is option (c) 12, 24, 24.

Note:
- Simply remember the formula that is $n + n = 2n$ here “n” is considered as male and female chromosome number and the 2n is the zygote chromosome number. Fertilization is the basic fusion after a fertilization event takes place and a zygote is formed, that has simply the double amount of chromosome number.
- The zygote genome basically contains the combination of the DNA present in each gamete. Zygote is considered as the earliest developmental stage. In case of single celled organisms, the zygote has the option of asexual reproduction by the mitosis to form the identical offspring.